Field investigation on the mechanical performance of corrugated steel utility tunnel (CSUT)

As a novel underground steel structure, corrugated steel utility tunnel (CSUT) has been considered as an effective alternative to traditional reinforced concrete utility tunnel. However, the current investigation of CSUT structure performance is urgently lacking. In this paper, a full-scale test was conducted to examine the mechanical perfor-mance and bearing capacity of a square arched double-cabin CSUT in soft clays using high-precision optical fiber sensing technology. Strains of all corrugated steel plates and typical bolts were monitored in real-time during the entire backfilling and loading processes, and also the crucial stress was compared with that calculated by circum-ferential compressive force method considering bending moment. Test results show that CSUT structure has not been damaged when backfill height is over three times the height of design. Stress of the top plate is much greater than that of other corrugated steel plates including crest section and trough section, and definitely becomes the most critical control factor for safety assessment, especially in the crown. The maximum plate stress is 375.7 MPa at backfill height of 10.0 m, which has not yet reached the yield strength of 390 MPa. Additionally, overlying soil generates a positive soil arch effect, which is conducive to improve applicability and bearing capacity. Bolt con-nection is feasible, but the construction process should be optimized. Simultaneously, numerical simulation method is used to analyze the influence of other parameters on CSUT. This study provides a significative reference for the popularization, construction, operation and maintenance of CSUT that is not currently common in China. (C) 2021 Elsevier Ltd. All rights reserved.